A post-marketing survey of efficacy of hymenoptera venom immunotherapy in the treatment of insect sting has been carried out. Three groups of patients who had previously experienced anaphylactic reactions following insect stings were evaluated for anaphylactic reactions following in- field stings: patients who achieved maintenance venom immunization (N = 380), patients on venom immunotherapy but who had not reached maintenance (N = 167) and patients who were followed but not treated. Severity of reactions were not different between the groups but frequency of in-field sting systemic reactions was inversely associated with venom dose administered. These data demonstrate the therapeutic efficacy of hymenoptera venom in reducing the risk of anaphylactic insect sting reactions.